This invention relates to a method and an apparatus for fabricating a rubberized wire sheet for use as steel breaker or steel ply for a vehicle tire.
As a method for fabricating a rubberized wire sheet for a tire breaker or tire ply, there has been conventionally adopted the topping calender method to be described hereinbelow. As shown in FIG. 8, two roller pairs 110 and 120 are arranged in a vertical direction. The roller pair 110 consists of two rollers 11. The roller pair 120 consists of two rollers 12. Two masses 10 of preheated rubber are supplied to the two roller pairs 110 and 120 respectively. Also, a predetermined number of wires 1 are fed between the roller pair 110 and the roller pair 120 after being arrayed by an array roller 14. Then, upper and lower surfaces of the predetermined number of wires 1 are pressingly coated with layers 15 of preheated rubber supplied along the surfaces of the rollers 11 and 12, thereby fabricating a rubberized wire sheet 16 having a desired width.
However, there are mainly the following problems in the topping calender method.
1. According to the topping calender method, the rubberized wire sheet 16 is fabricated by vertically sandwiching the plurality of wires 1 with the rubber layers 15 as shown in FIG. 9. The wire 1 is normally formed by twisting a plurality of filaments 1a. The respective filaments 1a are spaced from one another in every cross-section of the wire 1, thereby providing clearances 1e between the filaments 1a. Accordingly, there are some cases where the clearance 1e is left as it is without being filled by the rubber when the wire 1 is coated with the rubber layers 15. Further, clearance 1f between the respective wires 1 may be left unfilled with the rubber. A steel wire breaker rubberized according to the calender topping method experiences a problem similar to the above. Such a state allows the respective filaments 1a to move freely relative to one another, thereby disordering an array of the wires 1 and that of the filaments 1a. Particularly, this renders an array of the cords and adhesion thereof to the rubber unstable when the rubberized wire material is to be elongated in the cutting operation and the tire formation.
2. In the foregoing conventional topping calender method, topping accuracy can mainly be controlled based only on the amount of bank rubber. Accordingly, it is not easy to prevent disarray of wires before the topping and uneven thickness in the fabricated rubberized wire sheets.
3. In the foregoing conventional topping calender method, the rubber is required to have sufficient fluidity. Accordingly, it is difficult to rubberize the wire at a low temperature and a high speed.